The present invention relates to a recording apparatus utilizing a liquid developing medium toner and, in particular, to an electrophoretic recording apparatus.
A wet recording apparatus utilizing an electrophotographic structure including a photosensitive drum is known in the art. The photosensitive drum is charged and exposed to produce a static latent image formed thereon. The image is then developed in a liquid developer to form a readable image. Surplus developer stuck to the surface of the photosensitive drum is removed and a pigment image is transferred to a recording paper to be fixed thereon. Another known wet recording method utilizes a static latent image formed on a photosensitive recording paper developed in a liquid developer so that the image becomes fixed on the paper.
Further, an electrostatic recording apparatus is known in the art. A conventional electrostatic recording apparatus is such that a high voltage is impressed on an electrostatic recording electrode, a static latent image is formed on an electrostatic recording paper having a high resistance layer by corona discharge. The image is then developed in a developer. Surplus developer is removed and an image is fixed on the recording paper.
An electrophoresis method is known from U.S. Pat. No. 4,330,788 and "Electrophoretic Recording of Continuous Tone Images", Journal of Applied Photographic Engineering, vol. 6, June 1980. An electrode is moveable relative to a conductive recording medium within a developer. The developer contains solid particles a pigment made of solid particles suspended in a solvent. The solid particle migrate under the influence of an electric field towards the paper to form an image.
The prior art wet recording methods and apparatus have been satisfactory. However, they suffer from the following disadvantages. Utilizing a photosensitive drum inherently results in an apparatus which is very complicated and large in size. Additionally, the image deteriorates during the transfer process. The embodiment utilizing a photosensitive paper requires the use of expensive and special recording paper increasing the cost of use. Whereas, in the electrostatic reproducing apparatus, because a static latent image is formed through corona discharge, a continuous gradation of a pigment density is extremely hard to control. Accordingly, the toner (pigment) density is binary. Therefore, a half tone of inferior quality is produced during smooth tone reproduction in an area of toner gradation. Additionally, a static latent image forming member and developing member are formed as separate pieces resulting in an overly large apparatus.
The method for electrophoresis disclosed in U.S. Pat. No. 4,330,788 utilizing a line of an electric force extending from an electrode to an image carrier tends to spread. Therefore, an area larger than the sectional area of the electrode becomes developed and high resolution cannot be realized. Then, because the construction is such that the electrode moves in an orthogonal direction to that in which the image carrier is scanned and many electrodes cannot be packaged in a high density formation, a long time is required for obtaining a final image, thus limiting the speed of operation. Additionally, conductive recording paper must be used to obtain a high resolution again requiring a special paper.
Accordingly, it is desirable to provide an improved electrophoretic printer with electrodes configured to provide high resolution which overcome these problems associated with the prior art.